linux-kernel - [PATCH v2] cgroup:be able to remove the record of unplugged device

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Date:	Tue, 26 Jul 2011 08:37:26 +0800
From:	Wanlong Gao <gaowanlong@...fujitsu.com>
To:	Paul Menage <menage@...gle.com>
Cc:	Wanlong Gao <gaowanlong@...fujitsu.com>, lizf@...fujitsu.com,
	axboe@...nel.dk, linux-kernel@...r.kernel.org,
	wanlong.gao@...il.com
Subject: [PATCH v2] cgroup:be able to remove the record of unplugged device

Hi Paul:
How about this version?
Thanks

Write a record like:
echo 8:0 1000 > blkio.throttle.read_bps_device
to control the bps of the device.
And then unplug this device without doing
"8:0 0 > blkio.throttle.read_bps_device" to remove the record,
it will not be removed until reboot, because if the device is removed,
write some record will return "-ENODEV".

With this patch, when the device is removed, then if we want to remove
the record for this removed device, just write "0" then it'll not check
if it is a present device, just remove the present record.

Below is my test:
1. Test native.
[root@...t ~]# mount -t cgroup -o blkio nodev /cgroup/
[root@...t ~]# cd /cgroup/
[root@...t cgroup]# ll /dev/sd*
brw-rw---- 1 root disk 8, 0 Jul 25 13:27 /dev/sda
brw-rw---- 1 root disk 8, 1 Jul 25 13:27 /dev/sda1
[root@...t cgroup]# cat blkio.throttle.read_bps_device
[root@...t cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
[root@...t cgroup]# cat blkio.throttle.read_bps_device
8:0	1000
[root@...t cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
[root@...t cgroup]# cat blkio.throttle.read_bps_device
[root@...t cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
[root@...t cgroup]# cat blkio.throttle.read_bps_device
8:0	1000
[root@...t cgroup]# ll /dev/sd*
ls: cannot access /dev/sd*: No such file or directory
[root@...t cgroup]# cat blkio.throttle.read_bps_device
8:0	1000
[root@...t cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
-bash: echo: write error: No such device
[root@...t cgroup]# cat blkio.throttle.read_bps_device
8:0	1000

2.Test with this patch:

[root@...t ~]# mount -t cgroup -o blkio nodev /cgroup/
[root@...t ~]# ll /dev/sd*
brw-rw---- 1 root disk 8, 0 Jul 25 13:11 /dev/sda
brw-rw---- 1 root disk 8, 1 Jul 25 13:11 /dev/sda1
[root@...t ~]# cd /cgroup/
[root@...t cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
[root@...t cgroup]# cat blkio.throttle.read_bps_device
8:0	1000
[root@...t cgroup]# ll /dev/sd*
brw-rw---- 1 root disk 8, 0 Jul 25 13:11 /dev/sda
brw-rw---- 1 root disk 8, 1 Jul 25 13:11 /dev/sda1
[root@...t cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
[root@...t cgroup]# cat blkio.throttle.read_bps_device
[root@...t cgroup]# ll /dev/sd*
brw-rw---- 1 root disk 8, 0 Jul 25 13:11 /dev/sda
brw-rw---- 1 root disk 8, 1 Jul 25 13:11 /dev/sda1
[root@...t cgroup]# echo 8:0 2000 > blkio.throttle.read_bps_device
[root@...t cgroup]# cat blkio.throttle.read_bps_device
8:0	2000

[root@...t cgroup]# ll /dev/sd*
ls: cannot access /dev/sd*: No such file or directory
[root@...t cgroup]# cat blkio.throttle.read_bps_device
8:0	2000
[root@...t cgroup]# echo 8:0 0 > blkio.throttle.read_bps_device
[root@...t cgroup]# cat blkio.throttle.read_bps_device
[root@...t cgroup]# echo 8:0 1000 > blkio.throttle.read_bps_device
-bash: echo: write error: No such device
[root@...t cgroup]# echo 8:0 01100 > blkio.throttle.read_bps_device
-bash: echo: write error: No such device
[root@...t cgroup]#

Signed-off-by: Wanlong Gao <gaowanlong@...fujitsu.com>
---
 block/blk-cgroup.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index bcaf16e..4e81170 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -826,19 +826,19 @@ static int blkio_policy_parse_and_set(char *buf,
 
 	dev = MKDEV(major, minor);
 
-	ret = blkio_check_dev_num(dev);
+	ret = strict_strtoul(s[1], 10, &temp);
 	if (ret)
+		return -EINVAL;
+
+	ret = blkio_check_dev_num(dev);
+	if (ret && (temp != 0))
 		return ret;
 
 	newpn->dev = dev;
 
-	if (s[1] == NULL)
-		return -EINVAL;
-
 	switch (plid) {
 	case BLKIO_POLICY_PROP:
-		ret = strict_strtoul(s[1], 10, &temp);
-		if (ret || (temp < BLKIO_WEIGHT_MIN && temp > 0) ||
+		if ((temp < BLKIO_WEIGHT_MIN && temp > 0) ||
 			temp > BLKIO_WEIGHT_MAX)
 			return -EINVAL;
 
-- 
1.7.6

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